U.S. patent number 9,125,381 [Application Number 14/254,598] was granted by the patent office on 2015-09-08 for radial-shape wireless dog fence system and method with temperature compensated crystal oscillator for reduced clock speed variation between base unit and collar.
This patent grant is currently assigned to WOODSTREAM CORPORATION. The grantee listed for this patent is WOODSTREAM CORPORATION. Invention is credited to Jason Scott Gurley, Gary Roulston.
United States Patent |
9,125,381 |
Gurley , et al. |
September 8, 2015 |
Radial-shape wireless dog fence system and method with temperature
compensated crystal oscillator for reduced clock speed variation
between base unit and collar
Abstract
A radial-shaped wireless fence system is provided that contains
one or more dogs in a user-defined area without the need for a
physical fence or underground wire. The system includes a base unit
and at least one collar, and is easy to set up and use. Each of the
base unit and the one collar include a temperature compensated
crystal oscillator for reducing clock speed variation between the
base and collar units, preferably to +/-5 ppm, to effectively
eliminate communication errors between the base and collar
units.
Inventors: |
Gurley; Jason Scott (Madison,
AL), Roulston; Gary (Lititz, PA) |
Applicant: |
Name |
City |
State |
Country |
Type |
WOODSTREAM CORPORATION |
Lititz |
PA |
US |
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Assignee: |
WOODSTREAM CORPORATION (Lititz,
PA)
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Family
ID: |
48134914 |
Appl.
No.: |
14/254,598 |
Filed: |
April 16, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140305383 A1 |
Oct 16, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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13618329 |
Sep 14, 2012 |
8726845 |
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12926668 |
Oct 30, 2012 |
8297233 |
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61282727 |
Mar 23, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S
5/14 (20130101); A01K 27/009 (20130101); A01K
15/023 (20130101); A01K 15/04 (20130101) |
Current International
Class: |
A01K
15/04 (20060101); G01S 5/14 (20060101); A01K
27/00 (20060101); A01K 15/02 (20060101) |
Field of
Search: |
;119/712,718,719,720,721 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2008/085812 |
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Jul 2008 |
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WO |
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Primary Examiner: Williams; Monica
Attorney, Agent or Firm: Jacobson Holman, PLLC.
Parent Case Text
This application is a continuation of co-pending application Ser.
No. 13/618,329, filed Sep. 14, 2012, which is a continuation in
part application of prior application Ser. No. 12/926,668, filed
Dec. 2, 2010, which issued as U.S. Pat. No. 8,297,233 on Oct. 30,
2012, which claims the priority of U.S. Provisional application,
Ser. No. 61/282,727, filed Mar. 23, 2010, the priority of which is
hereby claimed.
Claims
What is claimed is:
1. A wireless boundary system for tracking a location of a movable
device in a generally circular user-defined roaming area
comprising: a base unit including a transceiver unit, a base unit
oscillator and a temperature compensated crystal oscillator (TCXO)
for reducing clock speed variation between a movable device and the
base unit, an output of said TCXO being used in place of an output
of said base unit oscillator, a location of said base unit defining
a center point of said generally circular user-defined roaming area
with a radius of said user-defined roaming area being defined by a
user during system set-up; at least one movable device trackable
within said roaming area, said movable device having a transceiver
unit in signal communication with said base unit transceiver unit,
said transceiver unit being incorporated within a PCB assembly that
includes a movable device oscillator and a movable device TCXO for
reducing clock speed variation between the movable device and the
base unit, an output of said movable device TCXO being used in
place of an output of said movable device oscillator; and said
system configured to continuously obtain distance values between
the base unit and the movable device on a real time basis using
said transceiver units and to calculate a current estimate of a
distance between the movable device in the roaming area and the
base unit on an ongoing basis.
2. The wireless boundary system as set forth in claim 1, wherein
said movable device is a collar worn by a dog that is being
contained within said user-defined roaming area, said movable
device oscillator and said movable device TCXO being mounted on
said collar.
3. The wireless boundary system as set forth in claim 2, wherein
said collar includes a correction unit that initiates
administration of a correction to the dog when the current estimate
calculated by the system indicates the dog is outside the roaming
area.
4. The wireless boundary system as set forth in claim 2, wherein
the TCXO of the base unit varies by a maximum of 50 Hz, conforming
to a specified clock speed tolerance of +/-2 ppm (64 Hz), when
subject to a temperature range of about 0.degree. C. to about
50.degree. C.
5. The wireless boundary system as set forth in claim 4, wherein
the TCXO of the base unit has a clock speed tolerance of 1.5 ppm at
room temperature.
6. The wireless boundary system as set forth in claim 2, wherein
the movable device TCXO mounted on the collar varies by a maximum
of 50 Hz, conforming to a specified clock speed tolerance of +/-2
ppm (64 Hz), when subject to a temperature range of about 0.degree.
C. to about 50.degree. C.
7. The wireless boundary system as set forth in claim 6, wherein
the movable device TCXO has a clock speed tolerance of 1.5 ppm at
room temperature.
8. The wireless boundary system as set forth in claim 1, wherein
said system is configured to weight and filter a plurality of said
continuously obtained distance values when calculating the current
estimate and to assign less weight to distance values considered
suspect due to disparity between said suspect distance values and
previously measured distance values and previously calculated
estimates of the distance between the movable device and the base
unit.
9. The wireless boundary system as set forth in claim 1, wherein
the TCXO of the base unit varies by a maximum of 50 Hz, conforming
to a specified clock speed tolerance of +/-2 ppm (64 Hz), when
subject to a temperature range of about 0.degree. C. to about
50.degree. C.
10. The wireless boundary system as set forth in claim 9, wherein
the TCXO of the base unit has a clock speed tolerance of 1.5 ppm at
room temperature.
11. The wireless boundary system as set forth in claim 1, wherein
the movable device TCXO varies by a maximum of 50 Hz, conforming to
a specified clock speed tolerance of +/-2 ppm (64 Hz), when subject
to a temperature range of about 0.degree. C. to about 50.degree.
C.
12. The wireless boundary system as set forth in claim 11, wherein
the movable device TCXO has a clock speed tolerance of 1.5 ppm at
room temperature.
13. A wireless fence system for containing a dog in a generally
circular user-defined roaming area by tracking a location of a
device that is movable with the dog, comprising: a base unit
including a transceiver unit and a temperature compensated crystal
oscillator (TCXO) for reducing clock speed variation between the
base unit and a movable device, a location of said base unit
defining a center point of said generally circular user-defined
roaming area with a radius of said user-defined area being defined
by a user during system set-up, an area outside said roaming area
constituting a trigger zone; at least one device movable with a
dog, said movable device having a transceiver unit in signal
communication with said base unit transceiver unit, said
transceiver unit being incorporated within a PCB assembly that
includes a movable device TCXO for reducing clock speed variation
between the movable device and the base unit; and said system
configured to continuously obtain distance values between the base
unit and the movable device on a real time basis using said
transceiver units and to calculate a current estimate of a distance
between the movable device and the base unit on an ongoing
basis.
14. The wireless fence system as set forth in claim 13, wherein
said movable device is a collar worn by a dog that is being
contained within said user-defined roaming area, said movable
device TCXO being mounted on said collar.
15. The wireless fence system as set forth in claim 14, wherein
said collar includes a correction unit that initiates
administration of a correction to the dog when the current estimate
calculated by the system indicates the dog is outside the roaming
area.
16. The wireless fence system as set forth in claim 13, wherein
said system is configured to weight and filter a plurality of said
continuously obtained distance values when calculating the current
estimate and to assign less weight to distance values considered
suspect due to disparity between said suspect distance values and
previously measured distance values and previously calculated
estimates of the distance between the movable device and the base
unit.
17. The wireless fence system as set forth in claim 13, wherein the
TCXO of the base unit varies by a maximum of 50 Hz, conforming to a
specified clock speed tolerance of +/-2 ppm (64 Hz), when subject
to a temperature range of about 0.degree. C. to about 50.degree.
C.
18. The wireless fence system as set forth in claim 17, wherein the
TCXO of the base unit has a clock speed tolerance of 1.5 ppm at
room temperature.
19. The wireless fence system as set forth in claim 13, wherein the
movable device TCXO varies by a maximum of 50 Hz, conforming to a
specified clock speed tolerance of +/-2 ppm (64 Hz), when subject
to a temperature range of about 0.degree. C. to about 50.degree.
C.
20. The wireless fence system as set forth in claim 19, wherein the
movable device TCXO has a clock speed tolerance of 1.5 ppm at room
temperature.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to the field of animal containment
and, more particularly, to a system and method for defining a
wireless dog fence that surrounds a user-defined area and for using
the fence to contain one or more dogs within the user-defined
area.
2. Description of the Related Art
Containing one or more dogs within a prescribed area has been
achieved in many different ways, most traditionally through the
construction of a fenced enclosure that is high enough to prevent
the dog from escaping the enclosure by going over the fence. Since
some consider above-ground fencing to be unattractive or otherwise
undesirable, "invisible" fence products have been developed that
rely on a wire buried underground that defines a desired "fence"
border for the dog or dogs. The wire transmits a signal that
activates a specially designed collar worn by the dog when the dog
comes within a certain proximity of the border. The collar, once
activated, can issue an audible warning and/or an electric shock to
the dog to ensure that the dog does not leave the "fenced-in" area.
Buried wire systems are labor intensive to install. Further, since
the wire may be unintentionally cut, or otherwise damaged, such as
by digging or tilling during lawn maintenance or the like, such
buried wire fence systems are also labor intensive when attempting
to find the location of the broken wire or other difficulty.
More recently, wireless fence products have been developed that
radiate a low frequency signal to saturate a spherical volume which
translates to a generally circular area on the ground plane. The
radius of the circle is user-definable and, according to one such
product manufactured by PetSafe, generally extends radially from
about 5 feet to about 90 feet. When the dog, while wearing a
specially designed collar, is "inside" the signal saturated area,
the collar receives a signal and no action is taken. When the dog
moves outside the signal area, however, the collar delivers a
correction signal.
Another wireless system is that marketed by Perimeter Technologies,
Inc. which, rather than creating a signal-saturated area, uses a
distance measuring technology between the collar and a base unit to
determine the range of the dog from the base unit. However,
interference created by objects often found within a household
environment can cause the collar and base to lose communication
with one another, resulting in artificially high range values
caused by attenuation or reflection, and/or undesired corrections
being delivered to the dog, i.e., corrections when the animal is
within the defined containment radius.
Precision matching of the clock rate or clock speed of the collar
and base components is also a problem. Normal RF practice for a
wireless fence circuit calls for +/-40 ppm for adequate control,
which equates to a clock speed of 32 MHZ+/-1280 Hz. However, this
level of control has been found to be inadequate to produce an
acceptable yield of product free of Received Signal Strength
Indication (RSSI) failures. RSSI failures occur when there is a
mismatch between the nominal 32 MHZ clock frequencies of the base
and collar components.
Accordingly, a need exists for an improved wireless fencing system
that is easy for the consumer to set up and use and that overcomes
the problems encountered with prior art systems.
SUMMARY OF THE INVENTION
In view of the foregoing, one object of the present invention is to
overcome the difficulties of containing a dog within a wireless
fence boundary without administering unwanted corrections to the
animal.
Another object of the present invention is to provide a wireless
fence system having a dual-antenna base unit and a dual-antenna
collar to improve the ratio of successfully received signal
transmissions to lost signals.
A further object of the present invention is to provide a wireless
fence system in accordance with the preceding objects in which
distance values are repeatedly obtained between the base unit and
the collar and then weighted and filtered to discount those
distance values likely to be errant and to track more accurately
the range of the dog from the base unit.
A still further object of the present invention is to provide a
wireless fence system in accordance with the preceding objects in
which NANOLOC.TM. chipsets are used in conjunction with a power
amplification circuitry to provide greater signal strength for
improved reliability in tracking the dog within the fence
boundary.
Yet another object of the present invention is to provide a
wireless fence system in accordance with the preceding objects that
provides increased precision in the control of the clock speed in
each of the base unit and collar so that these units can be
"matched" for a given clock speed.
A still further object of the present invention is to provide a
wireless fence system in accordance with the preceding objects in
which the NANOLOC.TM. RF circuitry of the collar and/or the base
unit is modified to include an external trimmable capacitor which
enables the oscillator frequency to be manually adjusted to achieve
a total range precision of 10 ppm (+/-5 ppm), which equates to a
clock speed of 32 MHZ+/-160 Hz, effectively eliminating
communication errors between the base unit and the collar of the
fence system.
Another object of the present invention is to provide a wireless
fence system in accordance with the preceding objects in which a
standard crystal oscillator within the NANOLOC.TM. RF circuitry of
the collar and/or the base unit is replaced with a temperature
compensated crystal oscillator (TCXO) to provide increased
precision in the control of the clock speed variation between the
base unit and the collar over a wide temperature range.
Yet another object of the present invention is to provide a
wireless fence system in accordance with the preceding objects in
which the tracking process of the system includes a normal battery
conservation mode and an accelerated mode during which the distance
value sampling rate is increased in response to the dog's proximity
to the fence boundary.
It is yet another object of the invention to provide a wireless pet
containment product that is user friendly and robust in operation
and which effectively tracks the distance between a base unit and
the dog to reduce the number of inappropriate corrections
administered to the dog.
In accordance with these and other objects, the present invention
is directed to a radial-shape wireless fence system for containing
one or more dogs in a user-defined area without the need for a
physical fence or underground buried wire. As used herein,
"radial-shape" refers to a generally circular area defined by a
border that encircles a center point defined by the location of the
base unit. The border represents an approximate area within which
the collar will begin to initiate a correction to the dog. This
border area marks the start of a trigger zone which extends
outwardly from the border in all directions to a distance at which
the collar can no longer receive input from the base unit. This
distance, and hence the "size" of the trigger zone, will vary
depending upon the terrain and objects between the dog and the base
unit, but can be as much as about a mile and a half from the base
unit in open flat country. The fence radius, which is set by the
user, is the distance between the base unit and the border and
defines a roaming area. As long as the dog remains within the
roaming area, signal transmissions are effectively sent and
received between the base unit and the collar to monitor the dog's
range from the base unit in real time, and no corrections are
issued to the dog. Under these conditions, the collar may be
configured to go to sleep to conserve battery power. In addition,
the system may be configured to filter out errant values and/or to
take no action if communication is suddenly blocked, such as due to
loss of power to the base unit or the collar, or the introduction
of a physical signal-blocking element to the system
environment.
Also as used herein, the "fence" is an estimated line that runs
concentrically with the border of the trigger zone. In the absence
of any interference or signal attenuation, the fence would be
circular, representing the circumference of a circle defined by the
radius. Due to real-world conditions, however, in which signal
interference is caused by various objects within the encircled
area, or objects anywhere that cause multipath effects, the
generally circular roaming area may have segments in which the
border or "fence" is closer to the base unit than at other
segments, i.e., segments in which the distance between the
border/fence and the base unit is less than the fence radius.
The system includes a base unit and at least one collar for a dog,
with multiple collars also being supported for additional dogs,
which is easy to set up and use. Both the base unit and the collar
have two antennas each, providing diversity to improve the ratio of
successfully received signal transmissions to lost signals. It is
advantageous if each of the base unit and the collar is provided
with a PCB-mounted component for reducing clock speed variation
between the base unit and the collar.
According to a first embodiment, the component for reducing clock
speed variation is a manually adjustable trimmable capacitor
incorporated within the RF circuitry of both the base unit and the
collar. The trimmable capacitor can be adjusted to obtain a closely
matched clock speed between the base unit and the collar, virtually
eliminating communication errors between these two units.
In a second embodiment, the component for reducing clock speed
variation is a temperature compensated crystal oscillator (TCXO).
The TCXO provides increased precision in the control of the matched
clock speed over a wide temperature range and thus is typically
most useful in the collar circuitry where the dog wearing the
collar may be indoors or outdoors. While the base unit may be
configured with either a trimmable capacitor as in the first
embodiment or with a TCXO, the trimmable capacitor is generally
preferred since the base unit is typically mounted indoors and
therefore is not subject to large temperature fluctuations.
The base unit is mounted inside the user's house or other desired
indoor location. By following a set-up menu on a display screen and
using input elements on the base unit, the user enters a desired
fence radius. The user then verifies the desired fence radius by
walking outwardly from the base unit with the collar, noting when
the collar outputs a signal indicating proximity to the trigger
zone and placing a flag or other marker at that location. The user
then walks back into the roaming area, moves laterally, and then
walks back outwardly until the collar again signals proximity to
the trigger zone at which point the user sets another flag or
marker. This process is continued until the complete border has
been marked with the flags or markers. Using these flags as visual
cues of the location of the "fence", and with the collar on the
dog, the user can then train the dog where the fence border is so
that the dog can be effectively contained therein.
Once the fence has been set up and the dog trained, the system
operates by continuously obtaining distance values between the base
unit and the collar in order to track the distance of the dog from
the base unit on a real time basis. These distance values are
weighted and filtered to discount those distance values likely to
be errant due to their disparity with previously measured values
and previous calculated estimates of the dog's position. More
particularly, through weighting and filtering of a plurality of
continuously obtained distance measurement values taken between the
base unit and the collar, anomalous measurement values are
discounted in terms of their contribution to the current estimate
of the dog's location. These filtering techniques in combination
with improved signal strength and antenna diversity in the
communication between the base unit and the collar improve the
accuracy with which the dog's range from the base unit is tracked
so that unwanted corrections are not administered to the dog.
These together with other objects and advantages which will become
subsequently apparent reside in the details of construction and
operation as more fully hereinafter described and claimed,
reference being had to the accompanying drawings forming a part
hereof, wherein like numerals refer to like parts throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the components of a radial-shape wireless fence system
in accordance with the present invention.
FIG. 2 illustrates the base unit shown in FIG. 1 as mounted inside
a house to define a roaming area and the trigger zone.
FIG. 3 illustrates the fence border and outlying trigger zone of
the system set-up shown in FIG. 2.
FIG. 4 is a flowchart showing the steps taken during the fence
setting mode of the system shown in FIG. 1.
FIG. 5A is an isolated view of the assembled collar shown in FIG.
1.
FIG. 5B is an exploded view of the components of the collar shown
in FIG. 5A.
FIG. 5C is a photograph of the first strap part of the collar strap
as shown in FIGS. 5A and 5B, and the antenna to be inserted into
the hole in an interior end of the strap part.
FIG. 5D is a photograph of the components shown in FIG. 5C after
the antenna has been inserted into the hole in the strap.
FIG. 5E is a photograph of the printed circuit board shown in FIG.
5B, as mounted in the lower housing and with the collar straps
connected thereto.
FIG. 5F is a photograph of the collar components shown in FIG. 5B,
without the battery, as the upper housing is brought into alignment
with the lower housing.
FIG. 5G is a photograph of the collar components shown in FIG. 5F,
as the upper housing is brought into engagement with the lower
housing to seal the correction unit compartment.
FIG. 5H is a photograph of the collar components shown in FIGS. 5F
and 5G with the correction unit compartment positioned for sealing
in an ultrasonic welding machine.
FIG. 6A is an exploded view of the components of a second
embodiment of a collar assembly including a collar strap and
correction unit for use with the wireless fence system according to
the present invention.
FIG. 6B is a top view of the collar strap shown in FIG. 6A.
FIG. 6C is a side view of the collar strap shown in FIG. 6A.
FIGS. 6D through 6J illustrate the sequential steps taken to
assemble the correction component and collar strap shown in FIG.
6A.
FIG. 7A is a block diagram of a portion of the collar PCB,
including the NANOLOC.TM. chipset, as configured without a
component for reducing clock speed variation.
FIG. 7B is a block diagram of the collar PCB shown in FIG. 7A in
which a component for reducing clock speed variation in the form of
a trimmable capacitor has been added in accordance with the present
invention.
FIG. 7C is a schematic of the circuit including the trimmable
capacitor as shown in FIG. 7B.
FIG. 7D is a block diagram of the portion of the collar PCB shown
in FIG. 7A in which a component for reducing clock speed variation
in the form of a temperature compensated crystal oscillator (TCXO)
has been substituted for one of the standard oscillators in the RF
circuitry in accordance with the present invention.
FIG. 7E is a schematic of the circuit including the TCXO shown in
FIG. 7D.
FIG. 7F is a more detailed schematic of the trimmer capacitor
circuit in accordance with the present invention.
FIG. 7G is a more detailed schematic of the TCXO circuit in
accordance with the present invention.
FIG. 8 is a flowchart showing the steps taken during the collar
setting mode of the system shown in FIG. 1.
FIG. 9 is a flowchart showing the steps taken during the ranging
process of the system shown in FIG. 1.
FIG. 10 is a flowchart showing the steps taken during the system
monitoring mode of the system shown in FIG. 1.
FIG. 11 is a flowchart showing the steps taken during the tracking
process of the system shown in FIG. 1.
FIG. 12 is a flowchart showing the steps taken during the
correction process of the system shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In describing a preferred embodiment of the invention illustrated
in the drawings, specific terminology will be resorted to for the
sake of clarity. However, the invention is not intended to be
limited to the specific terms so selected, and it is to be
understood that each specific term includes all technical
equivalents which operate in a similar manner to accomplish a
similar purpose.
According to the present invention generally designated by
reference numeral 10, a radial-shape wireless fence system is
provided that includes a base controller unit 12 and a remote unit,
generally embodied as a collar 14, as shown in FIG. 1. For the
purposes of training the dog and to provide visual markers for both
the dog and the user that generally correspond with the fence
border, a set of flags 16 is also preferably provided with the
system. The number of flags may be variable, but it is preferred to
have from about 25 to about 100 flags, depending upon the radius of
the containment or roaming area 32 (see FIG. 3) to be defined.
As shown in FIG. 2, the base unit 12 is intended to be positioned
within the user's home 18, garage, or other environmentally
controlled, indoor area, and is preferably configured to be mounted
on a wall. While it is possible to power the base unit with
batteries, it is preferably plugged into a properly grounded 120V
AC outlet. The base unit has two antennas 20, 21 for diversity when
communicating with the collar 14, a display screen 24 (preferably
LCD) and input elements or buttons, generally designated by
reference numeral 26, for inputting information to set up and
control the system. According to a preferred embodiment, the input
elements include up and down arrow keys 28, 29 and an enter button
30.
The base unit communicates with the collar using an integrated
circuit (IC) chip contained within the base unit and within the
collar. According to a preferred embodiment, the chipset is a
NANOLOC.TM. TRX 2.4 GHz transceiver chipset sold by Nanotron
Technologies of Berlin, Germany. The NANOLOC.TM. TRX 2.4 GHz
transceiver chipset is an IEEE 802.15.4a chirp spread spectrum
radio module with indoor and outdoor ranging capabilities. Other
chipsets that use the IEEE 802.15.4a chirping technique for radio
frequency distance measurement could also be used.
The base unit 12 is configured to enable the user to set up a fence
radius of from about 40 to about 400 feet. As noted previously, the
radius establishes the distance to the "fence" 31 (see FIG. 3)
which encloses the inner roaming area 32 and establishes the border
at which the trigger zone 34 begins. While the trigger zone appears
to be an annular area or ring 33 as shown in FIG. 3, the ring 33
actually represents the fact that there is generally some leeway or
cushion in the exact location of the border 31 as compared to the
fence radius set by the user, due to signal interference and
attenuation caused by real-world conditions as already noted.
Hence, the point at which a correction is actually initiated could
be within or on either the inner or outer edges of the annular area
33.
As summarized in FIG. 4, during the fence setting mode, the base
unit is located at the center of the desired radial-shaped area to
be set up, step 40. The user enters the desired fence radius into
the base unit, step 40, following a set-up menu displayed on the
display screen and using the input elements or buttons 26 to select
the desired parameters. Once the radius has been entered, the user
walks to the border with the collar to verify that the desired
radius has been set by noting where the collar reacts indicating
proximity to the trigger zone 34 and places a training flag at that
location to define the fence 31, step 42. The remainder of the
border or fence 31 is flagged off by the user as described in step
44.
As shown in FIGS. 5A and 5B, the collar 14 includes a strap
generally designated by reference numeral 50 that is fitted around
the dog's neck and a correction unit 52 mounted to the strap 50.
The strap 50 includes a first part 49 having holes therein that is
coupled to one side of the correction unit 52, and a second part 51
connected to the other side of the correction unit 52 which has a
buckle assembly 53 that can be engaged with the holes to secure the
collar 14 around the dog's neck.
The correction unit 52 includes a compartment 29 having a lower
housing 66 and an upper housing 54 with a cover 55 through which a
CR123A battery 56, for example, may be inserted into the
compartment 29 for providing power to the unit 52. The correction
unit further preferably includes an indicator light, preferably an
LED post 59 (see FIG. 5B) joined to the upper housing 54 with a
waterproof adhesive, that is visible from the outer side of the
correction unit and, like the base unit, the collar has two
antennas 60, 61 to provide diversity when communicating with the
base unit.
As shown in FIGS. 5C and 5D, the antenna 61 is preferably inserted
through an opening 46 and into a blind channel 47 in the collar
strap part 49 prior to final assembly of the collar and is secured
with silicone or similar material at the strap antenna insertion
points. Insertion of antenna 60 into a corresponding hole and
channel in strap part 51 is accomplished in like manner.
Housed within the compartment 29 of the collar correction unit 52
is a printed circuit board (PCB) assembly 65 as shown in FIGS. 5B
and 5E-5G. A NANOLOC.TM. TRX 2.4 GHz transceiver chipset like that
in the base controller is integrated with the PCB assembly 65 under
RF shield 39 (see FIG. 5E). The collar and base unit NANOLOC.TM.
chipsets send and receive radio transmissions from one another like
2-way radios. The NANOLOC.TM. chipsets are preferably enhanced in
operation with power amplification circuitry to provide greater
signal strength. When radio signals are sent from the antennas of
either the base unit or the collar to the other of the two
components, these signals propagate in an omni-directional or
spherical manner. Using these signals, the enhanced NANOLOC.TM.
chipsets perform a ranging process with their associated antenna
pairs which continuously captures, filters and refines the data to
yield the distance between the base unit and the collar at any
given time, as will be described further hereinafter.
Two probes 64 extend laterally from the lower housing 66 of the
compartment 29 that is against the dog's neck and are insulated
from the housing 66 by electrode grommets 63. Shorter probes 67 can
be interchangeably mounted to the lower housing 66 to better suit
short-haired dogs. Depending upon the setting of the collar, the
probes 64, 67 provide a physical correction signal to the dog upon
reaching the trigger zone. Alternatively, the collar can be set to
provide only an auditory correction signal to the dog. The physical
correction signal is preferably adjustable between a plurality of
levels to suit the size, age and temperament of the dog. In a
preferred embodiment, the collar defaults to a tone-only correction
signal.
To assemble the collar, the ends of the antennas 60, 61 that extend
out of the channels 47 are coupled to connectors on the PCB
assembly 65, preferably with a snap-on or push-on fit. The PCB
assembly is received within the lower housing 66 with the collar
strap parts 49, 51 on either side of the lower housing as shown in
FIG. 5E. The upper housing 54 is then brought into alignment with
the lower housing as shown in FIG. 5F, and then brought closer to
engage with the lower housing as shown in FIG. 5G. Once the upper
and lower housing are engaged with one another to ultimately close
the compartment 29, the correction unit 52 is sealed, preferably
using an ultrasonic welding machine 81 as shown in FIG. 5H. Once
fully assembled and welded as shown in FIG. 5A, the collar and
correction unit 52 are sufficiently waterproof so as to be able to
be submerged for a period of about one minute and thereafter
operate at or above 75% of accepted specifications for collar
performance.
The collar may also be embodied with a single strap 400 and a
modified correction unit 402 as shown in FIGS. 6A-6C, with the
strap being easily removable from the correction unit when
required. The antennas 404 projecting from each end of the
correction unit 402 are each enclosed within an insulating sleeve
to protect the antennas from environmental exposure. The bottom of
the correction unit 402 has two screw bosses 406 with insulators
408 onto which electrode grommets 410 and electrodes 412 are
secured when the collar is assembled.
In this embodiment, the single strap 400 has a center portion 414
with two spaced cutouts 416 for receiving the insulated screw
bosses 406 on the bottom of the correction unit 402. On either side
of the center portion 414, the collar is provided with a pocket
418, each pocket 418 receiving one of the sleeved antennas 404
extending from the correction unit 402 when the collar and
correction unit are assembled. The strap 400 includes a first end
420 and a second end 422 that are provided with complementary
fastening elements to allow the ends 420, 422 of the collar to be
secured to one another when the collar is being worn by a dog, as
is known in the art. The collar strap may be made of various
materials including leather, nylon, polymers, etc., as would also
be known by persons of skill in the art.
Assembly of the correction unit 402 to the collar 400 of the
embodiment shown in FIGS. 6A to 6C is summarized in FIGS. 6D-6J.
First, the electrodes 412 and electrode grommets 410 are removed
from the screw bosses 406 and the boss insulators 408, as shown in
FIG. 6D. The collar strap 400 is positioned with the cutouts 416 in
the center portion 414 aligned with the screw bosses 406 on the
bottom of the correction unit 402, as shown in FIG. 6E. The sleeved
antennas on the correction unit are inserted into the pockets 418
of the collar strap, as shown in FIG. 6F, and the bosses 406 with
insulators 408 are inserted through the cutouts 416, making certain
that the insulators 408 are inside the cutouts as shown in FIG. 6G.
One electrode grommet 410 is then slid onto each screw boss 406
until both grommets 410 are in abutment with the collar strap, as
shown in FIG. 6H. An electrode 412 is then screwed onto each screw
boss 406 while ensuring that the electrodes 412 are inside the
center depression of the grommets 410, as shown in FIG. 6I. Proper
assembly of the collar and correction unit is then verified to
ensure that the collar is ready for use, as shown in FIG. 6J.
As shown in FIG. 7A, the PCB assembly 65 of the collar includes a
PCB 65 with a NANOLOC.TM. chipset 158, a first crystal oscillator
160 and a second crystal oscillator 162. The first oscillator 160
and the NANOLOC.TM. chipset are shielded by a tuner can 168.
According to a preferred embodiment, the first crystal oscillator
has a frequency of 32 MHZ and the second crystal oscillator 162 has
a frequency of 32 KHz. Crystals having other frequencies could also
be used as would be understood by persons of ordinary skill in the
art.
Crystals such as the first and second oscillators 160, 162 are
manufactured to deliver their specified frequency with a specified
amount of external capacitance. However, manufacturers can only
realistically deliver a certain amount of precision for a given
price. Therefore, it is necessary to minutely adjust the
oscillation frequency to meet certain critical applications, such
as the ranging requirements of the present invention, which
requires a high degree of precision, preferably +/-5 ppm, for the
system to operate reliably. According to the present invention,
this high degree of precision is obtained by modifying the PCB
assembly in one or preferably both of the base unit and the collar
to include a component for reducing clock speed variation between
the base unit and the collar.
According to a first collar modification embodiment shown in FIGS.
7B, 7C and 7F, the component for reducing clock speed variation is
a trimmer component, preferably a trimmable capacitor 166. As used
herein, the terms "trimmer capacitor", "trimmable capacitor" and
"trimmer" are used interchangeably. The trimmer capacitor is used
to fine-tune the frequency variation of the first crystal
oscillator 160.
The resonant frequency of the crystal oscillator is affected by its
internal series resonant capacitance and parallel parasitic
capacitance external to the series circuit due to the proximity of
conductors that connect to the crystal itself. The resonant
frequency is also determined by the series resonance which is
mechanically determined by the physical dimensions of the
piezoelectric crystal itself.
The internal series resonant capacitance (Ci) is very small, on the
order of femto or atto farads, much less than the external parallel
capacitance (Ce) which is usually in pico farads. Since both
capacitances are in series with respect to the motional/series
inductance, moderate changes in the much larger external
capacitance have a very small effect on the total capacitance (Ct).
The formula for capacitances in series is: Ct=1/Ci+1/Ce. As can be
seen, if the external capacitance (Ce) is orders of magnitude
larger, then its reciprocal becomes a very small fraction of the
total capacitance. Hence, the external parallel capacitance affects
the resonant frequency to a much lesser degree than the internal
equivalent series resonant capacitance (Ci), but is very useful for
fine adjustment of the resonant frequency.
Crystal oscillators as used in integrated circuits (ICs) typically
use a CMOS inverter 167 with inverting gain. A frequency
determining network, either LC, ceramic, or crystal resonator,
outside of the IC inverter and connected to both its output and
input, is used to control the frequency.
The requirements for oscillation are regenerative non-inverting
feedback and enough gain around the total loop to ensure
regeneration. The loop consists of the inverter 167 that supplies
the gain, and the external resonator 160 that feeds the inverter
output back into the inverter's input 169. The resonator is the
loss that the inverter must offset in order to oscillate. Since the
inverter 167 supplies inverting gain, the external resonator must
also invert the feedback so that the total loop is non-inverting.
To accomplish this feedback inversion, a circuit is configured that
has two external capacitors 171, 173 in units to tens of pF, both
to ground, and the resonator 160 across the top from input to
output. With this configuration, the circuit has the appearance of
the letter "pi" and is therefore referred to herein as a "pi
network". The two external capacitors in addition to the parallel
capacitance of the crystal resonator form the total external
parallel capacitance as mentioned above.
The circulating current in the resonator network is much larger
than any current that the inverter is capable of producing. Hence,
the loop current 175 dominates. When, at an instant in time, the
loop current 175 is clockwise around the pi network, the capacitor
171 on the left/input will be transitioning negatively, while the
capacitor 173 on the right/output is transitioning positively.
Thus, opposite sides of the pi network have opposite polarities of
signal. This is the necessary second inversion mentioned above as
needed for oscillation.
In order to minutely adjust the oscillation frequency to meet the
ranging requirements of the present radial wireless fence
invention, the three external capacitances, which constitute most
of the total parallel capacitance external to the resonator, can be
increased or decreased. If the frequency is too high, the
capacitance can be increased, and vice versa.
According to the first collar modification embodiment of the
present invention shown in the block diagram of FIG. 7B and in the
schematics of FIGS. 7C and 7F, an oscillator configuration with
specified pi network capacitances, such as that in a NANOLOC.TM. RF
circuit, may be obtained by adding a small trimmer capacitor 166
across the top of the pi network to adjust the frequency of the
first oscillator 160. Because the addition of the trimmer capacitor
166 will exceed the specified total capacitance for the pi network,
the capacitance of the pi network is reduced by double the amount
of the center capacitance of the trimmer. Doubling is necessary
because the two pi capacitors are in series, so that their total
capacitance is approximately half of the capacitor values. As an
example, the existing NANOLOC.TM. RF circuit uses two 18 pF
capacitors for the pi network. In order to use a 1-5 pF trimmer
having a center value of 3 pF, the capacitance of the pi capacitors
is reduced by twice that, or by 6 pF each for an actual value of 12
pF. As modified to include the trimmer capacitor, the circuit now
yields 20 ppm of total adjustment range, which enables the desired
degree of precision to be obtained.
The tuner can 168 shielding the NANOLOC.TM. chipset 158 and the
first oscillator 160 has insufficient room to house the trimmer
166. Therefore, the trimmer 166 is preferably mounted to the PCB 65
outside the can 168 and short wires or PCB traces 169 are brought
outside of the can to connect to the trimmer. The trimmer capacitor
166 can be secured to the PCB by gluing or soldering as would be
known by persons of ordinary skill in the art.
To set the trimmer 166, a frequency counter is connected to the
oscillator test point on the NANOLOC.TM. integrated circuit. The
trimmer 166 is then adjusted to bring the frequency of the first
oscillator 160 within specification (+/-5 ppm). Preferably, the
frequency of oscillator 160 is well within the +/-5 ppm
specification, allowing for some temperature related drift. Trimmer
capacitors suitable for use with the NANOLOC.TM. chipset as used in
the wireless fence system described herein are available from AVX
Corporation of Fountain Inn, S.C.
According to a second collar modification embodiment shown in the
block diagram of FIG. 7D and the schematics of FIGS. 7E and 7G, the
component for reducing clock speed variation is a temperature
compensated crystal oscillator (TCXO) 170. As compared with the
variation found when using a standard oscillator, such as that sold
by Hosonic Electronic Co. Ltd, as the first crystal oscillator 160,
the TCXO 170 provides reduced variation in the clock output of the
collar RF circuit when the collar is subjected to a range of
temperatures, Specifically, the clock output of the Hosonic crystal
oscillator may vary by as much as +/-15 ppm at room temperature.
When subjected to a range of temperatures, such as 0.degree. C. to
50.degree. C., the potential variation of the Hosonic crystal
oscillator is +/-30 ppm (+/-960 Hz). The TCXO 170, over the same
range of temperatures, preferably varies by a maximum of 50 Hz,
conforming to a specified clock speed tolerance of 4/-2 ppm (64
Hz). At room temperature, the TCXO 170 has a clock speed tolerance
of 1.5 ppm. TCXOs suitable for incorporation within the NANOLOC.TM.
integrated circuit as part of the collar circuitry of the present
invention are available from FOX Electronics of Fort Meyers, Fla.,
and Raltron Electronics of Miami, Fla., as well as other
manufacturers of electronics. The base unit may also be modified to
include a TCXO in place of the Hosonic oscillator.
To modify the collar circuitry to include the TCXO, the software in
the integrated circuit of the NANOLOC.TM. chipset is modified to
disable the resident circuit for the first crystal oscillator 160,
bypassing such circuit in order to use the output from the TCXO
directly.
The fence components of the present invention may be modified with
either the trimmer capacitor 166 or the TCXO 170 to minimize
communication errors between the base unit and the collar.
Modifying the collar with the TCXO is advantageous when the fence
system is being used in geographical areas that see significant
temperature variation with respect to indoor versus outdoor
temperatures in both summer and winter. The base unit is preferably
modified with the trimmer capacitor but may be equipped with a TCXO
instead when outdoor use is anticipated. It is also possible to
have a trimmer capacitor only in the collar, with no component for
reducing clock speed variation in the base unit, if the clock
speeds can be sufficiently matched.
The collar 14 is set up for use with the fence system of the
present invention using the base unit 12 as summarized in FIG. 8.
The consumer can use the base unit to add, delete or change
settings for the collar, step 70. To add another collar for another
dog, step 72, the user presses one of the input buttons 26 on the
base unit to place the base unit into a seek mode. When powered on,
the collar is programmed to listen for and respond to a signal from
an appropriate enabled device such as the base unit. Upon receiving
the collar's response signal, the base unit identifies the unique
media access control (MAC) address associated with the collar and
stores its identity. Collar correction levels and the on/off status
of the collar can also be changed using the base unit, step 74. In
addition, collars can be deleted using the base unit, step 76.
Once the collar has been set up and activated, the NANOLOC.TM.
chipsets perform their ranging function to determine the distance
between the base unit and the collar at any given time. The ranging
process is as described in connection with the NANOLOC.TM. chipset
on the NANOLOC.TM. website, and is summarized in FIG. 9. Ranging
occurs on an ongoing basis unless the collar is asleep. The collar
sleeps on lack of motion and wakes up when motion is detected by a
motion sensor, such as an accelerometer, integrated with the
collar.
In brief, the first antenna at the base unit determines a first
distance value between itself and the first antenna on the collar,
and then determines a second distance value between itself and the
second antenna on the collar. The second antenna at the base unit
then determines a third distance value between itself and the first
antenna on the collar, and then determines a fourth distance value
between itself and the second antenna on the collar. If all four
distance values are successfully determined, the actual distance
value used in terms of obtaining the current estimate of the dog's
location is the shortest of the four measured values. This ranging
process is more fully described in co-pending application Ser. No.
12/539,404, published as U.S. Publ. No. US 2010/0033339 on Feb. 11,
2010 ("the '339 application"). The '339 application is hereby
incorporated by reference and considered part of the instant
disclosure as if fully set forth herein in its entirety.
Having two antennas at each of the base unit and the collar
improves the ratio of successfully received signal transmissions to
lost signals as compared with single antenna systems. This improved
ratio is particularly helpful in a household environment in which
buildings, shrubs, vehicles and other objects can act to interfere
with and/or block signal transmissions. Blocked signals can result
in the unwanted issuance of a correction to the dog, i.e., the dog
is corrected even though still within the prescribed boundary, or
in escapes from the boundary if communication is sufficiently
blocked.
The double antenna system also provides for dead zone detection and
accommodation. A dead zone is defined as an area in which signal
transmission may be lost or compromised. If such dead zones are not
detected or otherwise taken into account, this omission can result
in an unwanted correction being issued to the dog as the system may
conclude from the lack of signal transmission that the dog is
outside the boundary. A fuller discussion of the dead zone feature
is set forth in the '339 application.
As summarized in FIG. 10, once set up, the wireless fence system 10
maintains a monitoring mode during which the base unit 12 displays
information relating to the status of the battery charge level of
the collar 14, the current distance value between the collar and
the base, and whether a breach is detected, step 80. The base unit
12 may be configured during set-up to sound an alarm when a breach
occurs. A breach is defined as having occurred when the distance
value between the collar and the base unit is greater than or equal
to the radius set up for the fence border, step 82. When a breach
occurs, the system enters a correction mode as will be described
further hereinafter.
To reduce the likelihood of an unwanted correction being
administered to the dog, the system according to the present
invention includes a tracking process which is summarized in FIG.
11. When performing the tracking process, a valid distance value is
stored in flash memory at the base unit, step 90. However, the base
and collar continually transmit and receive signals to calculate
updated distance values on an on-going basis to track the dog in
real time. During this ongoing process, particular distance values
taken at any given time may be slightly inaccurate with respect to
the actual location of the dog, indicating the dog to be in the
trigger zone when, in fact, the dog is still inside the roaming
area. These errant values, if taken on face value, would result in
an unwanted correction being administered to the dog. Hence, the
tracking process uses an improved Kalman filtering technique with
hysteresis to "smooth out" consecutive distance values so that
errant values caused by tolerances and attenuation will be ignored,
step 92, and a more accurate tracking distance value obtained, step
100, as will be described more fully hereinafter.
The tracking process includes a normal battery conservation mode
and an accelerated mode for the battery 56 of the collar 14.
Whether the battery conservation mode is appropriate depends upon
the difference between the distance value and the fence radius,
step 93. If the difference between the distance value and the fence
radius is greater than a threshold value, the tracking mode remains
in the normal battery conservation mode in which the current range
to the collar is checked every 500 ms, step 95. If, however, the
difference between the distance value and the fence radius is less
than the threshold value, indicating the dog to be nearing the
fence or border, the system enters a fast range mode in which the
range is checked every 100 ms, step 97. This use of different
sampling rates allows for greater battery conservation through less
frequent sampling when warranted by the dog's position without
sacrificing accurate tracking obtained through accelerated sampling
as the dog approaches the fence 31 and trigger zone 34.
As already described, the tracking process also continually
compares the distance value associated with the collar with the
fence radius, step 94, and, if the distance value is less than the
fence radius, no action is taken, step 96. If the distance value is
greater than the fence radius, however, a correction sequence is
commenced, step 98.
As summarized in FIG. 12, the correction process begins when the
base unit sends a command to the collar to correct, step 110. Upon
receipt of this command, the collar is activated and issues a
correction in the form of a tone and/or physical correction, step
112. The correction continues until a set time-out period has been
reached, step 114, or until the dog returns approximately 10 feet
within the roaming area, step 116. If the time-out period has been
reached, step 114, the correction stops, step 118. If the time-out
period has not been reached, step 114, and the dog has returned
within the roaming area, step 118, the correction also stops. If,
however, the time-out period has not been reached and the dog has
not returned, step 116, the correction continues, step 112. The
length of the time out period can be varied, but according to one
preferred embodiment the time out period is about 30 seconds. The
extent to which the dog must return within the roaming area before
the correction is stopped could also be more or less than 10 feet
according to system design and settings.
To perform the "smoothing out" of consecutive distance values to
avoid inadvertent correction of the dog, various types of filtering
algorithms may be employed to filter the distance values. In a
preferred embodiment, the system according to the present invention
uses an enhanced Kalman filtering technique such as described in a
paper entitled, "An Introduction to the Kalman Filter" by Greg
Welch and Gary Bishop in the Department of Computer Science at the
University of North Carolina at Chapel Hill.
As a means of further smoothing out consecutive distance values and
of detecting and ignoring anomalous values, the Kalman filtering
algorithm used according to the present invention assigns a weight
to each measured distance value according to the apparent
reliability or confidence of the measurement sample. The confidence
of the measurement sample is determined on the basis of a
comparison made between the currently measured distance value and
the previously estimated distance value as determined by the Kalman
filtering algorithm. If the difference between the currently
measured distance value and the previously estimated distance value
is greater than a predetermined threshold, then the currently
measured distance value is considered to be suspect, i.e., to have
limited confidence, and is given little weight. This situation may
be illustrated by the following example. The previously estimated
distance value between the dog and the base unit was 10 feet and
the currently measured distance value, taken a second later,
indicates the dog to be 30 feet away from the base unit. The
currently measured distance value would appear to be errant since,
clearly, the dog could not have covered that much distance in the
time that elapsed. A currently measured distance value that
represents a realistic movement change, i.e., that shows a position
change less than the threshold, is given greater weight when used
to calculate an updated estimated distance value from the base unit
to the dog.
The confidence of the measurement sample may also be evaluated
using both a comparison between the currently measured distance
value and the previously estimated distance value, and an output of
an accelerometer on the collar. If the delta between the currently
measured distance value and the previously estimated distance value
is large and "high" acceleration is also reported, then the value
is given greater weight, i.e., is considered more reliable. If, on
the other hand, a large range delta is accompanied by little or no
acceleration, then the value is given little weight or ignored as
likely representing a bad range value.
It should be noted that the converse of the above identified
relationship does not necessarily hold true. For example, a low
delta in range values does not become more or less reliable when
accompanied by low acceleration reporting due to the incidence of
tangential motion under high acceleration. But including the input
of the accelerometer may be beneficial when evaluating motion
radiating toward or away from the base unit.
The present invention further achieves enhanced robustness in
adverse conditions through strength enhancement of the signals
being exchanged between the collar and the base unit. This strength
enhancement, or signal amplification, allows the base unit and
collar to conduct the ranging and tracking processes more
accurately than is possible with just the conventionally configured
NANOLOC.TM. chipsets when operating in a household environment
where buildings, shrubs, vehicles, etc., can interfere with signal
receipt and transmission. According to a preferred embodiment,
power amplification circuitry is integrated to work with the
NANOLOC.TM. chipsets to provide greater signal strength.
The present invention may also be adapted to track the location of
children, as well as other types of animals, through appropriate
modification of the remote unit. For example, rather than a collar,
a child could wear a wrist bracelet as the remote unit. The wrist
bracelet is configured with a NANOLOC.TM. chipset like that in the
collar already described herein. The wrist bracelet would not have
a correction capability, however, but would provide continuous
location information to the base unit, including the boundary
breach alert signal, for use by the parent or other supervising
adult as may be appropriate. Similarly, a harness or collar
arrangement could be configured for other animals that, by
providing distance information to the base station, would allow the
owner to track the animal's location, with or without a correction
capability as appropriate.
The foregoing descriptions and drawings should be considered as
illustrative only of the principles of the invention. The invention
may be configured in a variety of ways and is not limited by the
dimensions of the preferred embodiment. Numerous applications of
the present invention will readily occur to those skilled in the
art. Therefore, it is not desired to limit the invention to the
specific examples disclosed or the exact construction and operation
shown and described. Rather, all suitable modifications and
equivalents may be resorted to, falling within the scope of the
invention.
* * * * *